用java写一个堆践程序

public class ArrayStack {
	Object[] m_elements;
	int m_size;
	
	public ArrayStack(int len) {
		m_elements = new Object[len];
		m_size = 0;
	}

	public ArrayStack() {
		this(50);
	}

	// insert onto stack 
	public void push(Object element) {
		m_elements[m_size] = element;
		m_size++;
	}

	// return and remove the top element 
	public Object pop() {
		if (!this.isEmpty()) {
			Object obj = m_elements[m_size - 1];
			m_elements[m_size - 1] = null;
			m_size--;

			return obj;
		} else {
			return null;
		}
	}

	// return the top element 
	public Object top() {
		if (!this.isEmpty()) {
			return m_elements[m_size - 1];
		} else {
			return null;
		}
	}

	// return 1 --> is empty 
	// return 0 --> is not empty 
	public boolean isEmpty() {
		return this.size() == 0;
	}

	public int size() {
		return m_size;
	}
}

使用链表实现(单链表) ：

public class Stacklist {
	Node m_header;

	int m_size;

	public void ListStack() {
		m_header = null;
		m_size = 0;
	}

	public void push(Object value) {

		m_header = new Node(value, m_header);

	}

	public Object pop() {
		if (!this.isEmpty()) {
			throw new RuntimeException("Stack underflow");
		}

		Object obj = m_header.element;

		m_header = m_header.next;

		return obj;
	}

	// return reference to most recently added elemenet
	public Object peek() {
		if (!this.isEmpty()) {
			throw new RuntimeException("Stack underflow");
		}

		return m_header.element;
	}

	public boolean isEmpty() {
		return this.size() == 0;
	}

	// return the number of the queue's elements;
	public int size() {
		return m_size;
	}
}

链表的需要用到一个结点类 Node.java 代码如下

public class Node {
	Object element;
	Node next;

	public Node(Object theElement) {
		this(theElement, null);
	}

	public Node(Object theElement, Node n) {
		element = theElement;
		next = n;
	}

	public Object getElement() {
		return element;
	}

	public void setElement(Object element) {
		this.element = element;
	}

	public Node getNext() {
		return next;
	}

	public void setNext(Node next) {
		this.next = next;
	}
}